Given:
[tex]\begin{gathered} 4x+y=-27 \\ 7x+7y=7 \end{gathered}[/tex]Find : Solution and number of solution.
Sol:.
[tex]\begin{gathered} 4x+y=-27\ldots\ldots\ldots\ldots\text{.}(1) \\ 7x+7y=7\ldots\ldots\ldots\ldots\ldots\text{.}(2) \end{gathered}[/tex]Subtract the equation (2) to 7 times of equation (1)
[tex]\begin{gathered} 7(4x+y)=-27\times7 \\ 28x+7y=-189 \end{gathered}[/tex][tex]\begin{gathered} eq(2)-eq(1) \\ 7x+7y-(28x-7y)=7-(-189) \\ -21x=196 \\ x=\frac{196}{-21} \\ x=-9.33 \end{gathered}[/tex][tex]\begin{gathered} 7x+7y=7 \\ 7(-9.33)+7y=7 \\ -65.33+7y=7 \\ 7y=72.33 \\ y=\frac{72.33}{7} \\ y=10.33 \end{gathered}[/tex]So here only one solution i.e. (-9.33,10.33)